With respect to the background of the invention it is to be noted that for delivering stents in the region of stenoses or lesions in a body vessel or for releasing medicaments in such body regions, catheters of different designs are used. US 2009/0018501 shows a balloon catheter, the balloon of which is coated with a medicament. The balloon is arranged in the manner of a rolling membrane between outer and inner shaft. When inserting the catheter into the body, the inner shaft is displaced relative to the outer shaft in the proximal direction so that the balloon is covered between outer and inner shaft. At the site of use, the balloon is then inflated by means of a pressure fluid, wherein the outer shaft is displaced relative to the inner shaft in the proximal direction and the balloon opens like a rolling membrane in a rolling and shearing manner and dilates. The problem here is the fact that during opening the rolling membrane balloon, the membrane of the same is subjected to very small bending radii and high shear forces so that the coating with the active ingredient can be peeled off the balloon in an uncontrolled manner. Moreover, when the balloon opens, or already on the way to the site of use, losses of active ingredients can occur.
In connection with the delivery of stents, US 2009/0259286 A1 shows a catheter with a stent which, during the insertion of the catheter, is retained in the contracted position underneath a sheath at the distal end. Said sheath is configured such that when the balloon dilates and thereby the stent expands, it breaks along a predetermined path. This requires a relatively complicated and error-prone design of the sheath. Accordingly, the positioning of the stent can be inaccurate.
Finally, from US 2005/0033402 A1, a delivery device for a stent is known wherein the latter is arranged and covered underneath a sheath during the insertion. For releasing the stent, the sheath is provided with a pull wire by means of which the sheath can be pulled away on the proximal side and accordingly, a release of the stent can be achieved. This, of course, requires an extremely complicated construction of the catheter. Further, the pull wire is susceptible to breaking. In this case, releasing the stent is not possible anymore.
In EP 0 596 145 B1, a method is described by means of which the retention force of the stent on the catheter is achieved by means of embossing the stent pattern under the influence of temperature. Because the balloon shortens under the thermal effect, the embedding with this method is only optimal in the case if the stent itself is embedded in the balloon under thermal effect and the stent is virtually “frozen” in the balloon material. For stents coated with medicaments, this method can only be applied as long as the glass temperature of the balloon material lies far below the degradation temperature of the medicament.
From U.S. Pat. No. 7,651,525 B2, a stent device is known in which a catheter has an outer sheath which extends from the distal to the proximal end and in the distal end region of which, a self-expanding stent is arranged on a dilatable balloon in the contracted state. To deliver the stent, the outer sheath is pulled back manually by a practitioner or by a mechanical actuation in the proximal direction relative to the stent. The latter is positioned in a body vessel while inflating the balloon and self-extracting at the treatment site.